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CCL REPORT NO. 198

INTERIM REPORT

EFFECT OF WATERON HYDRAULIC BRAKE FLUID

BY

SC L E A R I N 0 0 U s EJOR PFDURL S&TVIFC S B. JORDAN

TECHNICAL INFORmAI¶ON D• "OPY ViMcrOi•fehs Y 1966 D

DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED

U. S. ARMY COATING & CHEMICAL LABORATORYAberdeen Proving Ground

Maryland

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4 UNCIASSIFIED

CCL REPORT NO. 198

INTERIM REPORT

EFFECT OF WATER ON HYDRAULIC BRAKE FLUID

BY

CHARLES B. JORDAN

MAY 1966

AM4CMS CODE NO. 5025.11.80200

DEPARTMENT OF THE ARMY PROJECT NO.IC024401AI08

U.S. ARMY COATING AND CHEMICAL LABORATORYABERDEEN PROVING GROUND

MARYLAND

DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED

UNCLASSIFIED

i

j 1 S aIn Ter

The object of this study was to determine the effect of absorbedmoisture on the physical and chemical characteristics of polar typehydraulic brake fluids. Specific studies were carried out on the ef-fect of moisture on equilibrium boiling point, flash point, cold tem-

I perature viscosity. oxidation stability, and effect on rubber withseveral polar brake fluids of varying chemical composition.

Moisture produced the following effects - a. Boiling points arelowered in all brake fluids - drastically in so-called "high boiling"fluids. b. Flash points are increased. c. Cold temperature viscosi-ties are usually Increased. d. The stability of the brake fluid to-ward oxidation is decreased. e. Rubber swelling and softening is de-creased.

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TABLE OF CONTENTS

Page No.

TITLE PAGE .............................................. i

ABSTRACT ...................................... ........... i i

INTRODUCTION ........................... .. ....... ...... I

DETAILS OF TEST ......................................... - 2

RESULTS OF TEST ... ............................. 4 .......... 2 - 3

DISCUSSION ......... o........... .. .. .. .. 3 - 4

RECOMMENDATIONS ... ... . ....... . ....................... . 4

REFERENCES ................................... . 4

DISTRIBUTION LIST . .. ............ ..................... . 5 - 7

APPENDIX A . . ..................................... 8

Tables I - VI ............... 0...................0....... 8 -14

DD FORM 1473 ........ o o..... I........... 0....... ......... ... 15

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i. I NTRODUCT i ON

The U. S. Army Coating and Chemical Laboratory, Aberdeen ProvingGround, Maryland was authorized by AMC Directive, AMCMS Code 5025.11.802., dated 24 July 1964 to conduct research on hydraulic brake fluids.Much publicity has been given to the problem of moisture entering ve-hicle brake systems through absorption. This report contains datashowing the effect of moisture on different physical and chemical prop-erties of polar type brake fluids.

II. DETAILS OF TEST

A. Water in Brake Fluid from Vehicles in Operation - Brake fluidwas removed from the master cylinders of 35 military vehicles and 9civilian vehicles, selected at random at Aberdeen Proving Ground, Mary-land. No previous vehicle history %as available. Equilibrium boilingpoints were conducted according to the procedure outlined in FederalSpecification VV-B-680. The amount of water was determined by the KarlFischer Method (7).

B. Effect of Water on Boiling Point of Brake Fluids -. Ten brakefluids were selected representing fluids currently being used in mili-tary and civilian vehicles. Three of these fluids met Federal Speci-fication VV-B-680, two fluids met Military Specification MIL-H-13910A,and two fluids met Military Specification MIL-P-460L6A., and three werehigh boiling fluids meeting SAE Specification J70b - 70R3.

The original equilibrium boiling points were determined by theprocedure outlined in Federal Specification VV-B-680 and water contentof each fluid was determined by the Karl Fischer Method (7)- Waterwas added in 1% increments and equilibrium boiling points were deter-mined after each addition.

C. Effect of Water on -40*F. Viscosity of Brake Fluids -Viscosity of thirteen brake fluids were determined at -40°F. with andwithout 2% water added. Included were twelve fluids meeting FederalSpecification VV-B-680 and one fluid meeting Military SpecificationMIL-H-13910A. Several of the fuids were then exposed to a 65% rela-tive humidity at 80*F. for a period of 7 days. Water determinationswere made by the Karl Fischer Method (7) and -400 F. viscosities weretaken.

D. Effect of Water on Flash Point of Brake Fluids - Flash pointswere conducted on four brake fluids by the procedure outlined in para-graph 4.5.2 of Federal Specification VV-B-680. Included were threefluids meeting Federal Specification VV-B-680 and one fluid meetingMilitary Specification MIL-H-13910A. Water was added to the fluidsin 2% increments and flash points were determined after each adO'tion.

II

E. Effect of Water on Oxidation Stability of Brake Fluids -

Twelve brake fluids meeting Federal Specification VV-B-680 were sub-jected to the oxidation stability test outlined in paragraph 4.5.14of Federal Specification VV-B-680 except that it, one test 0.5% BenzoylPeroxide tvas added to the broke fluid and in the second test 0.5% Ben-zoyl Peroxide and 5% water was added. In the specification test, only0.2% Benzoyl is added. Th,; excess peroxide decreased the stability toborderline values so that the effect of water would be more evidentand more pronounced. The test specimen! were visually examined forevidence of corrosion (pitting. etching, discoloration) after ten daysstnrage at 158*F.

F. Effect of Water on Rubber Swelling and Softening - Rubberswelling and durometer hardness change was determined on ten brakefluids meeting Federal Specification VV-B-680 according to the pro-cedure outlined in paragraph 4.5.10 with and without 5% water added.Cups meeting MIL-C-14055B were used in this test.

Ill. RESULTS OF TESTS

A. Water In Brake Fluids from Vehicles in Operation - Boilingpoints and percent water are contained in Table I. It will be notedthAt the fluids from the military vehicles have picked up water inamounts ranging up to 4.85% with the average pickup on the 35 vehiclesbeing 2.40%. The civilian vehicles have picked up an average of 1.37%water. Boiling points on the military vehicles range as low as 2460 F.with 69% of the fluids boiling below the minimum requirements specifiedin Federal Specification VV-B-680. The new vehicles containing dia-phragms did not accumulate as much water as the other vehicles. How-ever, there a-re Indications that eventually the brake fluid In thesevehicles will pick up enough water to lower the boiling points intothe critical ranges.

B. Effect of Water on Boiling Point of Brake Fluids - Table IIshows the effect of water on the boiling points of the brake fluids.Small percentages of water drastically reduce the boiling points ofhigh boiling fluids. An excellent example is where 1% of water lowersthe boiling point of a brake fluid from 558*F. to 3840 F., a drop of1740. A fluid which originally boils at 322*F. only drops 16*F., uponthe addition of 1% water. Sly or seven percent water brings the boil-ing points of all brake fluids tested to the same value of 240 to250°F.

C. Effect of Water on -40*F. Viscosity of Brake Fluids - Ascan be seen in Table III, water increased the sub-zero temperatureviscosity of nine of the brake fluids. Fluids such as No. 11 whichoriginally have viscosities approaching the maximum allowable rangewould not meet specification requirements after water pick-up.

2

D E cc t of WaLt.. r- u a-1n rsPint of Goaa. rsiu,.. I-.,W i%shows that water increases the flash point of brake fluids. Theazeotropes formed between water and the brake fluid solvents flashat higher temperatures than the solvents alone.

E. Effect of Water on Oxidation Stability of Brake Fluids -

Water greatly reduces the oxidation stability of brake fluids, asshown in Table V. In the tests recorded in Table V, the level ofBenzoyl Peroxide was raised to the point where one of twelve brakefluids exhibited excessive corrosion of test specimens. Several ofthe other fluids were borderline. With added water, three fluidsshowed excessive corrosion of test specimens and nine of the twelvefluids showed inrreased corrosion over the cests without water.

F. Effect of Water on Rubber Swelling and Softening - Table VIshows that the addition of 5% water reduced the amount of rubberswelling and szftening in every test.

IV. DISCUSSION

The deleterious effect of water is getting much publicity inall committees dealing with brake fluids both in the Government andin industry. Modern brake system designers are attempting to over-come the problem of water pickup by certain mechanical means, suchas diaphragms in the master cylinders and more efficient boots inthe wheel cylinders. These devices slow down the water accumulationIn the system but do not eliminate it, so that in a matter of time,water will be absorbed.

If the frequency rate of low boiling brake fluid found in thepresent stLdy conducted at Aberdeen Provlng Ground is representativeof that which is in all military vehicles, a very real problem existsand definite measures should be taken to alleviate it. Sixty-nineper cent of the vehicles screened at Aberdeen Proving Ground containedbrake fluid in the master cylinders which boll below minimum standards.One source of information reported that fluid in the wheel cylindersaccumulates water more rapidly than fluid in the master cylinders.This means that the percentage of bad fluid is higher than 69% andthe problem is even more critical, since highest temperatures are re-corded in the areas surrounding the wheel cylinders and low boilingfluids are much more apt to vaporize.

Although the problem of low temperature viscosity is not as crit-ical as boiling point, difficulties can be expected in our northernstates during cold weather. Brakes of vehicles subjected to periodsof "cold-soaking"' will not operate properly If viscosities exceed themaximun values listed in the specifications. Power transmission andrelease is too slow.

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The problem of brake fluid stability is also becoming increas-ingly evident. During the past few years large numbers of reportshave been filed concerning gumming and corrosion of brake parts inmilitary vehicles. This report shows that the chemical breakdown ofthe brake fluid Is accelerated by the presence of water and studiestoward the solution of this specific area of difficulty should con-tinue.

V. RECOMMENDATIONS

The following possible phases of action should be considered:

A. The trend in brake design should continue toward deviceswhich eliminate or cut down the expos'ire of fluid to atmosphere andwater absorption.

B. Brake fluid formulation development should be directedtoward the use of less hygroscopic chemicals. Development of improvedstabilizing inhibitors should continue.

C. Brake system maintenance should be more frequent and

more thorough.

Vl. REFERENCES

I. Authority: AMC Directive, AMCMS Code 5025.11.802 dated 24July 1964.

2. Federal Specification VV-B-680, Brake Fluid, Automotive,dated 15 December 1964.

3. Military Specification, MIL-H-13910A, Hydraulic Fluid, Non-Petroleum Base, Automotive Brake, All-Weather, dated 15 May 1963.

4. Military Specification, MIL-P-46046A, Preservative Fluid,Automotive Brake System and Components, dated 26 August 1964.

5. Military Specification MIL-C-IL.055B, Cup, Hydraulic BrakeCylinder; Synthetic Rubber, dated 14 November 1961.

6. Society of Automotive Engineers Specification SAE J70b,dated December 1964.

7. Fischer, K.j, Angew. Chem 48, 394-6, (1935).

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TABLE III

EFFECT OF WATER ON -40 0 r VISCOSITY OF BRAKE FLUIDS

After 7 days atBrake Initial Values 2% Water Added 65% RH & 80OFFluid % -4O'F Total % -403F Total % -40°F

No. Water Viscosity Water Viscosity Water Viscosity

..43 684.5 2.43 621.8 ....

2 .24 912.3 2.24 1024.2 -- --

3 .19 1088.9 2.19 1193.0 6.57 1897.0

4 .38 1693 2.38 1363.7 ....

5 .32 1660 2.32 1440.8 ....

6 .!9 1311.5 2.19 1479.3 ....

7 .12 844 2.i2 907.5 5.38 1470.0

8 .24 1113 2.24 1216.8 -- --

9 .31 1421 2.31 1554.6 6.30 2327.0

10 .41 622.0 2.41 705.7 -- --

11 .54 1578 2.54 1872.0 --O..

12 .24 1082.2 2.24 1126.8 6.39 1632.0

13 .23 198.9 2.23 257.7 6.23 395.8

Fluids 1 - 12 meet VV-B-680

Fluid 13 meets MIL-H-13910A

SI

Ig r ............

TABLE IV

EFFECT OF WATER ON FLASH POINTS OF BRAKE FLUIDS

Brake Fluid Initial Flash Point Flash Point After Water Addition OF

No. OF* 2% 4% 6%

1 155 155 158 165

2 200 212 218 220

3 225 230 235 240

4 155 170 170 175

-'Average of 3 determinations

Fluids 1,2,3 meet VV-B-680Fluid 4 meets MIL-H-13910A

12

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TABLE V

EFFECT OF WATER ON OXIDATION STABILITYOF BRAKE FLUIDS - 10 DAYS, 158 0 F - WITH EXCESS BENZOYL PEROXIDE ADDED

InspectionBrake Fluid 0.5% Benzoyl Peroxide

No. 0.5% Benzoy1 Peroxide 0.5% Water

1 Fall Fail

2 Borderline Fail

3 Pass Borderline

4 Borderline Fail

5 Pass Borderline

6 Pass Borderline

7 Pass Borderline

8 Pass Pass

9 Pass Pass

10 Borderline Borderline

11 Pass Borderline

12 Pass Borderline

All fluids under normal test conditions meet VV-B-680.

13

TABLE VI

EFFECT OF WATER CONTENT ONRUBBER SWELLING AND SOFTENING

Rubber Swelling Rubber Softening(inches) (degrees)

Fluid No. w/o water +5% water w/o water +5% water

1 0.026 0.012 7 5

2 0,025 0.012 8 7

3 0.036 0.013 9 6

4 0.031 0.014 9 5

5 0.034 0.017 9 7

6 0.025 0.014 7 6

7 0.037 0.022 9 7

8 0.014 0.007 4 3

9 0.031 0.016 9 5

10 0.028 0.016 9 7

All fluids meet VV-B-680.

i

144

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U. S. Army Coating and Chemical Laboratory UnclassifiedAberdeen Proving Ground, Maryland Zb GRoup

3 REPORT TITLE

EFFECT OF WATER ON HYDRAULIC BRAKE FLUID

14 DESCRIPTIVE NOTES (Type of raport and incluiavo date&)Interim report

S AUTHOR(S) (Lost name. first rome, initial)

Jordan., Charles B.

6 REPORT DATE 7a TOTAL NO OF PAGES J7b NO OF REFS

May 66 j 7So. CONTRACT OR GRANT NO. Sa ORIGINATOR'S REPORT NUMBER(S)

AMCMS Code No. 5025.11.80200 CCL #198b. PROJECT NO.

IC02W401A108C 9b. OTHER REPORT NO(S) (Any other numbers that may be a&signed

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Qualified requesters may obtain copies of this report from Defense DocumentationCenter. Distribution of this document is unlimited.

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U. S. Army Materiel CommandWashington, D. C. 20315

13 ABSTRACT

The object of this study was to determine the effect of absorbed moisture onthe physical and chemical characteristics of polar type hydraulic brake fluids.Specific studies were carried out on the effect of moisture on equilibrium boilingpoint, flash point, cold temperature viscosity, oxidation stability, and effect onrubber with several polar brake fluids of varying chemical composition.

Moisture produced the following effects - a. Boiling points are lowelred inall brake fluids - drastically In so-called "high boiling' fluids. b. Flashpoints are increased. c. Cold temperature viscosities are usually increased.d. The stability of the brake fluid toward oxidation is decreased. e. Rubberswelling and softening Is decreased.

I

DD IJoRM 1473 UnclassifiedSecurity Classification

A• L .Z, - - -

UnclassitiedS tctltv ll I ."l ssifitat to• l

U - --- - -- .... ... I ..{ _t1141C A 4 sq e LaL!%KEY WORDS ______ROLE~ WT R4OLE1VT 1

Moisture absorptionBrake fluidsFlash pointsStabilityRubber swellingBoiling po!'.L

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